Carriers of S1P include albumin and apolipoprotein M; in serum, S1P is important in vascular homeostasis and immune cell response.33, 34 There are precedents for osteoblast‐derived S1P as potentially protecting cancer proliferation,35 but at present physiological levels of S1P in bone and regulation of its production in vivo are not well characterized. This evidence concerns the gene APOM and cancer.